In the fabrication of semiconductor wafers, it is often necessary to change the orientation of a silicon wafer as the wafer is translated between processing stations and/or from a wafer carrier. In some processing applications, for example, a wafer is dipped into a number of vertical processing chambers and/or stations, such as for megasonic cleaning, even though other processes such as deposition and lithography may require the wafer to be in a horizontal orientation. Vertical chambers that can be used to perform one or more of these surface processing and preparation steps are described, for example, in U.S. Pat. No. 6,726,848, entitled “APPARATUS AND METHOD FOR SINGLE SUBSTRATE PROCESSING,” filed Dec. 7, 2001. As horizontal orientation is presently the standard, since wafers typically come in a FOUP as known in the art, it becomes necessary for the automation mechanisms of the processing system to rotate the wafers between horizontal and vertical orientations as needed during transfer. In many of these processing systems, the large chambers used to transfer and orient wafers pose a number of problems, such as the need for complex transfer devices and elevator mechanisms that require a significantly larger volume than otherwise would be necessary. Currently, six axis robots are used that occupy a relatively large space and have an undesirable amount of complexity. In addition to occupying additional space on the floor of the fab, the larger internal volume leads to longer purge cycles necessary to remove potential contaminants such as moisture and oxygen. These longer purge cycles result in a decrease in system throughput. The use of complex transfer mechanisms and elevator mechanisms also reduces system uptime, and further increases the risk of contamination due to the generation of particles during movement of the transfer components.
The cost of processing semiconductor wafers is often evaluated by the amount of throughput per unit cost, as well as the throughput per square area of floor space used for the processing apparatus. Therefore, a processing system with a larger overall footprint is considered to have a higher cost per area. Another cost factor is the capital cost of the equipment, which increases as the apparatus becomes more complex.